View Full Version : New Laundry Room

11-23-2011, 12:21 AM
Greetings, everyone.

I'd like to tap into an existing DWV system to add a clothes washer standpipe, but I'm not sure how best to do it. We use the California Plumbing Code here.

There is a bathroom on the other side of the wall, with two vents running in the common wall. Ideally, I could tap into the 2" WC vent and wet vent the WC with the standpipe's drain if that's allowable. Another option I see is to tap into the vent only for vent purposes and drain to a 2" cleanout below the floor. I hesitate to drain below the floor because it will require either more exposed DWV piping or obliterating an already heavily cut sole plate on the common wall.

Can I simply tap into the WC vent and wet vent that line?

I hope the photos are self explanatory.

Many thanks for your help.



Other side of wall


11-23-2011, 01:05 AM
More questions:

Will the (gas) dryer provide ventilation for the 5x6 room by blowing air to the outside and drawing fresh air in under the door? I will be using a front-loading washer, so steam from around a top loader lid won't be an issue. It seems like the room should stay fairly dry unless I string a clothes line in there.

Also, I would like to tee off the 3/4" black gas pipe in the crawlspace below. Is it kosher to install a tee with a union as long as the crawlspace is well vented and everything is accessible (after a short belly crawl)? If so, what kind of union should I get?

11-23-2011, 03:01 AM
The washer puts out too much water to wet vent over anything.

The washer needs a seperate waste line and p-trap.
You could install with a fixture cross that is 2" on the bottom and with a sink, having the vent at the same level, but not using a toilet vent as the drain line.

11-23-2011, 06:27 AM
You have to provide combustion air supply for a gas dryer. The space under the door may not be enough. You may have to use a louvered door, or at least put a vent grill in the door.

11-23-2011, 11:41 AM
Thanks for the replies, Terry and jimbo.

To clarify the setup, I've created the diagram below.

I don't think a fixture cross is what I want, since there is no drain in the wall, only two vents.

I guess what I should do is tie into the drain below, the easiest being the 2" bath cleanout, then tie into the vent in the wall. Can I tie into either the 1.5" vent or the 2" vent?

What is the minimum distance from the standpipe's sanitary tee until the first bend in the vent above? Is a 5-6 ft trap arm ok for the 2" washer standpipe?

I gather I cannot place the standpipe's P-trap under the floor because the extra height might wash out the trap water?

I like the idea of the louvered door instead of simply a door cut. Unfortunately, I just hung a new door yesterday! I think going with a louvered door is best though.

Any thoughts on whether I can install a gas pipe union and tee in the vented crawlspace? Is there a specific type of union?


11-23-2011, 03:22 PM
(Only because that's a vented crawlspace I feel compelled to comment...)

That's about the least-effective batt-insulation job I've seen in awhile, with so many gaps & compressions that it can't be performing much better than 50% of rated R. And since the plumbing penetrations aren't foam-sealed you have a significant infiltration drive going on as well. To hit it's rated R it needs to be in contact with the subfloor above, at full loft, and it needs a bottom side air-barrier (that should be vapor permeable, but air-tight. Housewraps usually fill the bill, but definitely NOT poly sheeting) Without a bottom side air-barrier and air-sealing the floor that fiberglass is nearly useless.

In a more humid climate than yours that scene would be a nearly guaranteed mold problem, but summertime dew points in the Bay Area are quite low compared to the eastern US seaboard (or most of the right-half of the US lower 48), so you can get away with it, but it's sub-optimal.

A better (and possibly easier) solution would be to convert the crawl into a conditioned space by sealing the foundation walls from the slab all the way up & over the foundation sill & band joist to the subfloor with spray polyurethane foam, and sealing all the vents. A less money/more DIY-labor solution would be to do it with rigid foam insulation.

It looks like somebody put some decently fat insulation on the hot water distribution plumbing though.

11-23-2011, 04:38 PM
Dana, you could not imagine the curse words I've thrown while under that house. Everything looks like it was cobbled together by children, and the "insulation" is no exception. That house is extremely cold, with terrible infiltration from the holes below and from the 30 or so can lights riddled with holes above. When the bathroom fan runs, it smells like a rat's nest from a previous infestation we had in the crawlspace. I could go on and on about how I'd like to choke every tradesman who touched that house and every inspector who didn't. The insulation fixes will come after the laundry room is done.

Gary Swart
11-24-2011, 09:24 PM
The bright side of the insulation is the pro insulation companies are surprisingly inexpensive when compared to other trades such as electricians, plumbers, and carpenters. This is because they can get a heck of a lot of insulation placed in a very short time, and the supplies (insulation) is not overly expensive. NOTE: This statement is not to imply that the trades I used as examples are overpriced, it's just that their work takes longer to do and the materials are usually much more costly.

11-28-2011, 01:24 PM
DO go with the conditioned-sealed crawlspace approach, ESPECIALLY with the stack effect of all of those can-lights! It's not a gazillion board-feet- a 2" shot of closed cell foam (~R12) does wonders. In my neighborhood for jobs less than 1000 board-feet I'd be paying ~$1.20 per inch per square foot, which is comparable to kit-pricing.